Difference in the susceptibility to certain molluscicides and Schistosoma mansoni infection of three forms Egyptian Biomphalaria glabrata.

The first generation of 3 morphologically different forms of B. glabrata collected from Giza were compared for LC50 values susceptibility to bayluscide and copper sulphate (chemical molluscicides) and Anagallis arvensis and Calendula micrantha (plant molluscicides) and to Schistosoma mansoni infection. Form (2) as juvenile and adult were less sensitive to C. micrantha and A. arvensis. Form (3) as juvenile and form (1) as adult were least sensitive to CuSO4. Approximately the same susceptibility to bayluscide was observed in the 3 forms either as juvenile or adult. The sublethal concentrations of the molluscicides on B. glabrata 3 forms showed no significant difference in the growth or survival rate in between. Form (2) was significantly higher in the egg lying capacity. The total protein concentration was not affected except in certain cases where the increase was primarily due to the increase in the globulin concentrations which indicate with the marked increase observed in the urea concentration and marked increase or inhibition in the activity of either AST or ALT that the digestive gland of the 3 forms of snails is seriously affected by molluscicides. The 3 forms of B. glabrata showed low susceptibility to infection with the local strain of S. mansoni.

Bioactivity of Anagallis arvensis and Calendula micrantha plants, treated with ammonium nitrate, superphosphate and potassium sulphate fertilizers, on Biomphalaria alexandrina.

The survival rate of B. alexandrina snails maintained in aqueous solutions of the two tested plants (Calendula micrantha and Anagallis arvensis) decreased gradually with time until the 9th week and 10th week where the survival rate was zero in the high concentration of A. arvensis and C. micrantha, respectively, meanwhile, the survival rate of the control was 20%. Also, the two plants caused reduction in hatchability of snails egg masses. Thus, the percent of hatching in A. arvensis (82 ppm) was 46% and in C. micrantha was 72% compared with control (97.29%). Both plants reduced the infection rate of Biomphalaria alexandrina snails with Schistosoma mansoni miracidia to 41.17% and 61.9%, respectively, compared with control (90%). C. micrantha caused much higher reduction in snail infection rate than A. arvensis. The prepatent period was significantly prolonged in snails maintained at higher concentration of both plants. The cercarial output (expressed as mean number/snail) revealed that, A. arevensis caused a significant reduction in cercarial production than control. While, high concentration (120 ppm) of C. micrantha caused a significant elevation in the mean number of cercariae/snail. However, the total number of cercariae produced by all snails in each group showed a reverse relation with the tested concentrations in both plants.

Studies on the molluscicidal action of some isatin derivatives against Biomphalaria alexandrina in Egypt.

Some compounds selected from the isatin derivatives and their metalleted products were used to study their molluscicidal effect on Biomphalaria alexandrina. The results indicated that some of these compounds showed good results and seem to be promising molluscicides.

Effect of UV-irradiation, gamma irradiation and praziquantel on infected Biomphalaria alexandrina snails.

Schistosomiasis control represent the main target of many research programme allover the world. Effect of physical (UV- and gamma-irradiation) treatment as well as chemical (PZQ) treatment on infected laboratory bred Biomphalria alexandrina snails have been studied. Gamma irradiation and PZQ-treatment induced high rate of mortality than UV-irradiated and non-treated control snails. The cercarial production was severely reduced as a result of UV-, gamma-irradiation and PZQ-treatment. Pre-patent period was significantly increased in gamma-irradiated and PZQ-treated groups than UV-irradiated and control groups. Gamma irradiation and PZQ-treatment showed severe effects on hermaphrodite gland and cercariae. Trials of experimental infection in swiss albino mice revealed that low rate of infection (9.7% and 1.3%) was induced by cercarial shedding from UV-irradiated and PZQ-treated snails respectively. Whereas, cercarial production of gamma-irradiated snails failed to induce infection in swiss mice.

Effect of X-ray on the snails of schistosomiasis in Egypt.

Biomphalaria alexandrina and Bulinus truncatus snails were exposed to sublethal doses 0.2, 3, 5, 10 and 20 rad of X-ray. The survival and reproductive rates of these snails were highly affected by these doses. The maximum survival periods of laboratory populations of Biomphalaria snails were less than those of field ones which means a high sensitivity of laboratory snails to X-ray. The reproductive capacity of irradiated Biomphalaria and Bulinus snails was highly suppressed and this will interrupt Schistosomiasis transmission. A deleterious effect of gametogenesis of irradiated Biomphalaria was histologically proved. After 3 weeks of snail irradiation with high dose (40 rad) the hermaphrodite gland became completely evacuated.